Process for dewaxing and refining oils



Allg. l, H. N. LYONS PROCESS FOR DEWAXING AND REFINING OILS Patented Aug. l, 1933 1,929,922 Y PROCESS Fon DEWAXNG AND REFINING onJ Henry N. Lyons, South Orange, N. J., assigner to Doherty Research Company, New York, N. Y., 'a Corporation of Delaware Application Apri1`29, 1929. serial No; 358,795

2 Claims.

This invention relates to a process for separating'A wax from` oils, particularly wax distillates and residuum, also the relining of such oils. i

f In prior processes for dewaxing oils several' 5, methods have` been employed, all of which require long periods of time or expensive rmachinery, for ,separating wax. For example, `in the coldsettling process, previously filtered stock is -mixed with naphtha, slowly cooled and allowed to stand until the amorphous wax or petrolatum settles to the bottom of the precipitation tanks. These tanks are usually heavily insulated and provided with cooling coils since approximately four days arerequired for the settling of the wax before a separation can be made. Furthermore, considerable care must be taken in getting a proper blend between the stock and the naphtha used for dilution. Recently this cold-settling process has been considerably improved by the use -of centrifugal separators for` the removal of the wax from the oil following the chillingstep. The centrifugal separator however can operate successfully onlyon the separation of amorphous wax, so that even now the crystalline wax is sepa- 1 rated by previously known methods, as by chilly ing the wax stock tor below Rand then passing it through lter presses.v The use of iiltery presses however entailsconsiderable outlay for the quantity of oil treated, and` furthermore requiresmore labor. been vfound necessary to double-press the oil in order to completely free the same of wax.

In attempting to separate crystalline wax from oil by use of a centrifugal separator, after the wax has been precipitated in the oil, it was found that thewax could not be successfully removed from the separator becauserofthe formation of layers of hard wax on the interior of the separator bowl and the accumulation of solid wax in the wax discharge orices and collecting pans.

An object of the present invention is, therefore, to rprovide a process and method of operation which will rapidly and elciently effect the which contain amorphous wax or inhibitors which do not permit the wax to crystallize, and stocks without lthe use of complicated and expensive equipment.'

comprises the chilling of the wax stock sufciently to precipitate the waxtherein and then effecting a rapid settling of the wax byfa mechanical thickening operation.

5, Further objects and advantages of the invention will vbe apparent from the following descrip. h

In certain cases also it has H,rernovaljof wax from wax-bearing distillates4 In accordance with this object, the inventionv tion taken in connection with the accompanying drawing in which?r The iigure is avdiagrammatic view largely in vertical section of anvapparatus adapted to carry out the various steps of the` process.

According to the invention, the oil to be treated, which may be crude oil, cutstock, cut distillates or residuurn, Ais passed from storage (not shown) or a decolorizing .system described hereinafter, blended with naphtha andl introduced through a pipe 2 into an externally insulated heat exchanger 4 wherein the fresh charging stock passes countercurrent to cold dewaxed oil from a later step of the process. In the heat exchanger 4 the -fvresh charging stock passesthrough a coil or coils 6 and is finally delivered v through a pipe 8 into Y a mixing rchamber 10 wherein the partially cooled oil which has been blended. with naphtha or other suitable diluting agent for the purpose of lowering its cold' test may be mixed with other oil or additional quantities of diluting agents introduced through a valved pipe i2.` f.

The mixing chamber 10 is heavily insulated as shown and provided with a mechanical stirrer 14 anda hopper 16, the latter of which maybe used for the introduction of a iilter aid such as filter cel" or such materials as diatomaceousv earth, decolorizing clay .ori fullers earth. The chamber. 10 may be sufficiently large to accom-r modate aconsiderable batch for mixing'purposes," or the materials introduced throughthe inlets 8, 12and 16 maybe introduced in the proportions desiredfso that the mixing chamber is used continuously. The partially chilledoil or vmixture of oil and other materials passes from the" chamber -10 through the valved pipe 18, and is forced by pump 20 through a valved pipe 21 into and through cooling coils 22 mounted in an insulatedchiller 24. A'Ihis Chiller is preferably op. erated in connection with a refrigerating plant so that either cold brineV or ammonia is introduced through a pipe 26 and passed counter-current to the ow of the oil through the coils 22. The

cooling agent is withdrawn from the vchamber 245 through a-pipe 28 and conductedback to the re--l frigerating plant.

In passing through the coils 22 the wax containing stock is cooled to a temperaturegbetween zero and 10 F., so that the wax, either amorphous or crystalline, is precipitated in the oil.

' From the coils 22 the chilled oillmixture is delivered through a valved pipev 29 into abus pipe conducting the precooled oil through a'valve tain much larger proportions of solidimaterials pipe 35.

The thickener 34 as shown in the drawingV comprises a tank of comparatively large diameter with respect to its depth .and is provided with'V a sloping conical bottom. It is also equipped with a mechanical thickening mechanism comprising a central shaft 36 provided at lits upper end with a drive gear 3,8 and at its lowerend with sweeps 40: which upon rotation ofV the lshaft v36 causes the ystratification of the oil and wax in the chamber 34 and themovement of the wax towardY the center'ofthe chamber. The lower end of the'shaft 36 is providedwith a short screw conveyor 42 "which extends into the wax outlet 44..

`The oil-'wax mixture delivered through pipes 32A entersA the thickener near its vcenter and through a Vslow'operation of the sweeps 40 the oil-fwaxV mixture is carried downy yin the center of the chamber so that the .wax is rapidly precipitated and the claried oil caused to rise around oil' collected in the trough 46 vis conducted by a pipe 48 anda pumpj50, through a pipe 52 into i the heat exchanger 4, where the oil passes in heat- Y Y exchange with fresh charging stock as previously referred' to. ered through4 a pipe 54, and passed to storage or toa reducing still.r

The separated wax passing through the outlet 44 contains somewhat more oil than is usually found inlter press wax; thereforeit is conducted by means of a Vscrewconveyor 56 into a second thickener 58, constructed andoperated in f substantially the sameV manner as the thickener 34 described above. Y, The thickener A58 however need notbe as large indiameter as the thickenerl 34. since the materials introduced therein conto be separated. 'I'he thickener 58 may be con- 'from several Yof the. thickeners 34. The sepa- Vrated'oil collected in the trough 46 of separator 58 is passed through a pipe 60, pump 62, pipe 64,l

@lsshown and also heavily insulated. In con- *structing an apparatus for a large dewaxing plant, the thickeners may be made of concrete j and built in the ground so Vas to provide for small heat losses, or cooling coils 68A may be mounted in the insulation material so as to maintain a comparatively low temperature. The thickener 58 may be constructed in a similar manner as shown,

and both thickeners are preferably provided with'.

In carrying out the process withcertain stocks tween the oil and its wax content is small, it isV proposed to mix with the oil in the mixing chamber 10, a quantity of filter aid such as lter cel or clay,v the particles of which will form nuclei for the precipitation of wax in the coils 22 and separators 34. In such a case the filter aid causes the formation of comparatively large particles of wax and therefore gives a much more rapid separation of the oil in the separators 34. When the addition of filter aid is delayed until the wax has been precipitated in the oil by adding the filter aid in the mixer 33, thevvax particles attach themselves to thev particles of lter aid and thereby separate more easily than the Wax would alone.

The invention further includes a combined process ofdecolorizing and dewaxing oils in a single operation; In accordance with this procedure the residuum or wax distillate to be treated is introduced into the chamber 10 through the pipe '12, and therein mixed with from 15 t0 30% (preferably 20%) of 1GO-mesh clay introduced 95 through'the hopper '16. The oil-clay mixture thus formed is conducted through the pipe 18, and'passed bypump 20"anda valved' pipe 72, through a heater 74 wherein the oil-clay mixtureA a is raised to a temperature of about 460 F. YFromf 100 78 in which the moisture content of the mixture is allowed tofescape through a vapor pipe 80. The, oil and clay-mixture passing to the bottom of the separator 781s conducted by a pipe 82- and pump 84 through a cooling coil in a heat exchanger 86, and nallyV through a valved pipe 88 into the pipe4 2.

During this operation'the Valves in pipes 2, 8..

' and 21 are closed and the valves in pipes l88, l35'1510 and29 are left open.

The oil-clay mixture introduced into the pipe 2 from pipe 88 now passes through the heat ex- The separated oil is finally deliv;

"ofil'and clay mixture is cooled to a temperature rsuiiicient to precipitate the wax content of the oil onto the4 particles of clay. In the chambers 34 the oil is separated from the wax and clay in the manner previously described. This combined'lzo decolorizing and dewaxing' procedure has many advantages, chief of which are the maintenance ofthe oil and clay mixture without separation of the clay during thewhole operation, and the ease of separating both the clay and wax from the oil without expensive filters or centrifuges,

or the use'of high pressures. During this operation, diluting naphtha'may be introduced with the oil or through the valve in pipe 2. Y My present methods lubricating stocks which arev subjected to contactltration with decolorizing clays must bepassed throughlter presses 'in vorder to remove'the clay vfrom the o`il. In

the present process and in accordancewith the` Apresent, invention the clay is much more eiiiciently and rapidly separated-from the oil by the mechanical action in the separatorsv 34. If clesired the separated clay may be filter-pressed or steamed to remove the small amountof oil it may4 contain. I

In adopting the present invention forfuse4` in plants for dewaxing oils, the principal part of the equipment necessary Aoutside that already VAcoritained in the plant, will be the mechanical-separating units 34 and 58 which are inexpensive vto construct and easy to operate'.-

Having `thus described the invention in its a preferred form, what is claimedr as newl is: in whichA the difference in specific gravity be- 1 VAn apparatus for the treatment of petrole@j um Yoil with clay, comprising a heater, a vapor 150 separator and a refrigerating unit,r means for passing a mixture of oil vand clay through said heater and into said vaporseparator from the latter of which Water vapor is permitted to escape, means'for` passing the oil-clay mixture from said separator through said refrigeratingunt to pre- "cipitate the Wax in the oil, and means for separating the Wax and clay from said oil comprising a settlingjchamber equipped with mechanif rapid separation of theroil;

cal thickening lelementsV adapted to 2. The process. of refining and dewaxing lubrieating oil stocks, which comprises mixing the oil effect thev ening operation.

stock to be treated with a rening clay, heating the mixture in a confined stream to a tem- HENRY N. LYoNs.

izov 

